Method for producing metal alcoholates

Abstract

Process for preparing metal alkoxides by means of transalcoholization, wherein a lower metal alkoxide is fed via a side feed into a reactive distillation column comprising a rectifying section situated above the feed and a stripping section situated below the feed; a higher alcohol is fed into the stripping section, the bottom and/or a bottoms circuit of the column; a solution of a higher metal alkoxide in the higher alcohol is taken off at the bottom of the column and/or from the bottoms circuit; and a vapor comprising lower alcohol is taken off at the top of the column, the vapor is at least partially condensed and a substream of the condensate is recycled to the top of the column as reflux. The process enables the preparation of metal alkoxides with a reduced energy requirement.

The invention claimed is: 
     
       1. A process for preparing metal alkoxides by means of transalcoholization, wherein
 a lower metal alkoxide is fed via a side feed into a reactive distillation column comprising a top, a bottom, a rectifying section situated above the feed and a stripping section situated below the feed; 
 a higher alcohol is fed into the stripping section, the bottom and/or a bottoms circuit of the column; 
 a solution of a higher metal alkoxide in the higher alcohol is taken off at the bottom of the column and/or from the bottoms circuit; and 
 a vapor comprising lower alcohol is taken off at the top of the column, the vapor is at least partially condensed and a substream of the condensate is recycled to the top of the column as reflux; 
 
       wherein the higher alcohol has a higher boiling point than the lower alcohol. 
     
     
       2. The process according to  claim 1 , wherein the higher alcohol is fed into the bottom and/or the bottoms circuit of the column in liquid form. 
     
     
       3. The process according to  claim 1 , wherein the solution of the higher metal alkoxide comprises not more than 1.0% by weight of the lower alcohol, based on the total weight of the solution of the higher metal alkoxide. 
     
     
       4. The process according to  claim 1 , wherein the solution of the higher metal alkoxide comprises 3% to 60% by weight of the higher metal alkoxide, based on the total weight of the solution of the higher metal alkoxide. 
     
     
       5. The process according to  claim 1 , wherein the column has a forced circulation evaporator and the higher alcohol is fed in liquid form into the feed to the forced circulation evaporator. 
     
     
       6. The process according to a  claim 1 , wherein the top condensate comprises not more than 0.8% by weight of the higher alcohol, based on the total weight of the top condensate. 
     
     
       7. The process according to  claim 1 , wherein the lower metal alkoxide is fed in as a solution in the lower alcohol and the solution comprises 20% to 40% by weight of the lower metal alkoxide, based on the total weight of the solution of the lower metal alkoxide. 
     
     
       8. The process according to a  claim 1 , wherein the lower metal alkoxide is an alkali metal alkoxide. 
     
     
       9. The process according to  claim 8 , wherein the lower metal alkoxide is a sodium alkoxide or a potassium alkoxide. 
     
     
       10. The process according to  claim 9 , wherein the lower metal alkoxide is sodium methoxide or potassium methoxide. 
     
     
       11. The process according to  claim 1 , wherein the higher alcohol is selected from isopropanol, sec-butanol, 2-methyl-2-butanol, tert-butanol, 2-methyl-2-pentanol, 3-methyl-3-pentanol, 3-ethyl-3-pentanol, 2-methyl-2-hexanol and 3-methyl-3-hexanol.